Ultrasonic welding tools

ABSTRACT

In an ultrasonic welding tool of the kind comprising a relatively fixed frame, which supports an assembly including a transducer for converting electrical energy into ultrasonic vibrations, and a velocity transformer carried by the transducer for altering the amplitude of the vibrations produced by the transducer, the assembly is supported against lateral movement relative to the frame, by engaging an axially extending portion of the assembly, which is of substantially uniform cross section, as an axially sliding fit in a bearing, which is fixed relative to the frame in use, so as to support the assembly against lateral movement relative to the frame.

Continuation-impart of application Ser. No. 688,548, Dec. 6, 1967.

ULTRASONIC WELDING TOOLS [56] References Cited UNITED STATES PATENTS 2,991,594 7/1961 Brown etal 51/59 3,054,309 9/1962 Elmore et al. 228/1 3,056,192 10/1962 Jones 29/4701 X 3,184,841 5/1965 Jones et al. 228/] X 3,429,028 2/1969 Maropis et al.. 228/] X 3,492,847 2/1970 Ustyantsev et al 228/1 X Primary ExaminerJohn F. Campbell! Assistant ExaminerR. J. Craig Attorney-Holman & Stern ABSTRACT: In an ultrasonic welding tool of the kind comprising a relatively fixed frame, which supports an assembly including a transducer for converting electrical energy into ultrasonic vibrations, and a velocity transformer carried by the transducer for altering the amplitude of the vibrations produced by the transducer, the assembly is supported against lateral movement relative to the frame, by engaging an axially extending portion of the assembly, which is of substantially uniform cross section, as an axially sliding fit in a bearing, which is fixed relative to the frame in use, so as to support the assembly against lateral movement relative to the frame.

This invention is a continuation-in-part of my application Ser. No. 688,548, filed Dec. 6, 1967.

The invention relates to ultrasonic welding tools of the kind comprising a relatively fixed frame, an assembly including a transducer, secured to the frame by resilient means, for converting electrical energy into ultrasonic vibrations, and a velocity transformer carried by the transducer for altering the amplitude of the vibrations produced by the transducer, the velocity transformer being adapted to support a sonotrode shaped to engage a workpiece, and the assembly being supported against lateral movement relative to the frame.

In tools of the kind specified it has been the practice to support the assembly against lateral movement by clamping the transformer relative to the frame. However, since in use the transformer is subject to longitudinal vibrations it is necessary to attach the clamp to the transformer accurately at a position where a node occurs when the transformer vibrates.

Such arrangements are cumbersome and where it has been desired to produce a tool having a plurality of adjacent transducers and associated transformers and sonotrodes the proximity of the transducers and therefore of the sonotrodes has been governed by the spacing of the clamp arrangements.

According to the invention in a tool of the kind specified, the assembly is provided with an axially extending portion of substantially uniform cross section, said portion being received as an axially sliding fit in a bearing which is carried by said frame and which is fixed in use with respect to the frame. so as is support said assembly against lateral movement relative to the frame.

In the preferred example said axially extending portion is part of the velocity transformer. It is found that improved results are obtained if in this preferred embodiment, the transducer is also provided with an axially extending portion of substantially uniform cross section which is received as an axially sliding fit in a second bearing.

In the accompanying drawings FIG. l is a sectional view of an ultrasonic welding tool in accordance with one example of the invention, FIG. 2 is a view similar to FIG. ll of a modification of the tool shown in FIG. 1, FIG. 3 is a perspective view of a compound arrangement of a plurality of the tools shown in FIG. l, and FIG. ll is a sectional side view illustrating another example of the invention.

Referring first to FIG. 1 of the drawings, there is provided a fixed frame 1111 having secured thereto, by way of a resilient mounting lltl, a transducer 112 for converting electrical energy into ultrasonic vibrational energy. The transducer 112 has engaged therewith a velocity transformer 13 for increasing the amplitude of the vibrations produced by the transducer. The transformer 13 includes a cylindrical shank M which is received as a sliding fit in a sleeve 15 secured to the frame 1111. At its free end the shank 14 carries a sonotrode is which in use traps a workpiece against a relatively fixed anvil.

in use, as the tool operates the shank 1a is free to reciprocate axially within the sleeve 15 to transmit ultrasonic vibrations to the sonotrode 116, but is held against lateral movement which would result in lateral movement of the sonotrode relative to the workpiece.

Owing to the high frequency of the reciprocation of the shank, it is desirable, in order to avoid excessive heating of the sleeve l5, for the sleeve to be constructed in a material having low energy absorption properties, for example a material such as polytetrafluoroethylene. It will be appreciated that since the shank l4l slides in the sleeve 15 the positioning of the sleeve with respect to a vibrational node in the transformer is not critical. However, it is advantageous to position the sleeve l so that a vibrational node occurs in the transformer within the sleeve so that the sleeve and the shank are subject to the minimum relative movement.

In the modification shown in FIG. 2 the sleeve is mounted in a spherical member 17 which is received in a corresponding spherical recess in the frame and through which the axis of the sleeve can be inclined with respect to the frame.

In addition, the transducer ll2 is adjustably secured to the frame and so the working position of the sonotrode can be altered without the necessity of altering the position of the frame. The spherical recess in the frame ill is defined in part by a locking ring 118 which can be tightened to lock the member 117 and consequently the sleeve 15 in the given position.

As the use of the sleeve ll5 results in a compact assembly it will be appreciated that where a plurality of transducers with their respective sonotrodes are required adjacent one another, the proximity of sonotrodes is governed by the dimensions of the transformer and transducer, thereby permitting the sonotrodes to be positioned closer to each other than is possible with certain prior constructions. Such a compound arrangement is shown in FIG. 3 and comprises a plurality of transducers 12 with their respective transformers l3, sleeves 15 and sonotrodes 16, which are mounted in a common frame 1 la.

Referring now to FIG. 4i, there is provided a fixed frame 1111 which at its upper end incorporates an inverted cup-shaped part 1113 secured to the main portion of the frame and con stituting part thereof. There is further provided a transducer 11112 for converting electrical energy to ultrasonic vibrational energy, the transducer 1112 having engaged therewith a velocity transformer 113 for increasing the amplitude of the vibrations produced by the transducer H2. The transformer H3 includes a cylindrical shank llM which is received as a sliding fit in a sleeve 1H5 secured to the frame lllll. At its free end the shank lid carries a sonotrode lllo which in use traps a workpiece against a relatively fixed anvil.

The transducer M2 is also formed with an axially extending portion 109, the portion 109 being accommodated within the part 112 in sliding engagement with a cylindrical bearing 1108. The upper end of the portion 109 is spaced from the base of the part 1112 by resilient means lit], and the assembly 1109, 11112, 113, 1M, 1116 is locked against rotation by a pin 1107 extending from the part 118 through the resilient mounting into the portion 109, material 1117 having low energy-absorbing properties being provided around the portion of the pin 107 within the portion 109. Preferably the length of the portion 109 is one-fourth wavelength.

In use, as the tool operates the shank 1114 is free to reciprocate axially within the sleeve 1115, and the portion R09 is free to reciprocate axially within the bearing 108. However, the assembly is held against lateral movement which would result in lateral movement of the sonotrode lilo relative to the workpiece. It is preferable, in view of the high frequency of the reciprocation of the shank, for the sleeve i115 and the bearing 10a to be constructed in a material having low energy absorption properties, for example polytetrafluoroethylene. The use of such a material avoids problems due to overheating, and it will be appreciated that by virtue of the arrange ment described using the sleeve 1115 and bearing 11%, the positioning of the sleeve i115 and bearing 108 with respect to a vibrational node in the assembly is not critical. However, it is advantageous to position the sleeve M5 and bearing 1108 so that vibrational nodes occur within the sleeve i115 and bearing 108, because in this way the sleeve H5 and bearing 108 are subject to minimum relative movement.

The example described is a modification of FIG. l, but the other examples can be modified in a similar manner.

Means other than the pin H07 could be used to prevent rotation of the assembly 109, 1112, 113, 1114, 116. For example a fixed bar could be used, the bar having polytetrafluoroethylene studs which press against the sonotrode ll 16.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

ll. An ultrasonic welding tool comprising a relatively fixed frame, an assembly including a transducer for converting electrical energy into ultrasonic vibrations, resilient means mounting the transducer on the frame, a velocity transformer carried by the transducer, the velocity transformer altering the amplitude of vibrations produced by the transducer, and being arranged to support a sonotrode shaped to engage a workpiece, and a bearing arrangement supporting the assembly against lateral movement relative to the frame, the bearing arrangement including a first part constituted by an axially extending portion of the velocity transformer, said portion being of substantially uniform cross section, and being received as an axially sliding fit in a second part of the bearing, the second part being carried by the frame and being fixed in use with respect to the frame, so that the bearing supports the said assembly against lateral movement relative to the frame.

2. A tool as claimed in claim 1 wherein said second bearing part is constituted by a sleeve, formed in a material having low energy absorbing properties.

3. A tool as claimed in claim 1 wherein said second bearing part is formed in polytetrafluoroethylene.

4. A tool as claimed in claim 1 wherein said assembly is adjustably mounted in said frame and said second bearing part is mounted in the frame in such a manner that the second bearing part can be moved so that its axis is tilted with respect to the frame.

5. A tool as claimed in claim 1 including a plurality of assemblies and bearings supported in a common frame.

6. An ultrasonic welding tool as claimed in claim I in which the transducer is also formed with an axially extending portion of substantially uniform cross section, said portion of the transducer being received as an axially sliding fit in a second hearing which is carried by said frame and which is fixed in use with respect to the frame. 

1. An ultrasonic welding tool comprising a relatively fixed frame, an assembly including a transducer for converting electrical energy into ultrasonic vibrations, resilient means mounting the transducer on the frame, a velocity transformer carried by the transducer, the velocity transformer altering the amplitude of vibrations produced by the transducer, and being arranged to support a sonotrode shaped to engage a workpiece, and a bearing arrangement supporting the assembly against lateral movement relative to the frame, the bearing arrangement including a first part constituted by an axially extending portion of the velocity transformer, said portion being of substantially uniform cross section, and being received as an axially sliding fit in a second part of the bearing, the second part being carried by the frame and being fixed in use with respect to the frame, so that the bearing supports the said assembly against lateral movement relative to the frame.
 2. A tool as claimed in claim 1 wherein said second bearing part is constituted by a sleeve, formed in a material having low energy absorbing properties.
 3. A tool as claimed in claim 1 wherein said second bearing part is formed in polytetrafluoroethylene.
 4. A tool as claimed in claim 1 wherein said assembly is adjustably mounted in said frame and said second bearing part is mounted in the frame in such a manner that the second bearing part can be moved so that its axis is tilted with respect to the frame.
 5. A tool as claimed in claim 1 including a plurality of assemblies and bearings supported in a common frame.
 6. An ultrasonic welding tool as claimed in claim 1 in which the transducer is also formed with an axially extending portion of substantially uniform cross section, said portion of the transducer being received as an axially sliding fit in a second bearing which is carried by said frame and which is fixed in use with respect to the frame. 